1. Field of the Invention
The present invention relates to an audio synthesis system, especially to an audio synthesis system applied in communication apparatuses.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a wavetable audio synthesis system 10 of the prior art. The wavetable audio synthesis system 10 of the prior art comprises a music database 11, an analysis module 12, a music generator 14, a digital/analog converter/amplifier 20, and a speaker 22. While the wavetable audio synthesis system 10 of the prior art synthesizes a music file 13, the music database 11 transmits the music file 13 to the analysis module 12, and the analysis module 12 selects music data and control commands (including the selection of the instruments, the setting of the volume and special efficacy, etc.) for the music file 13 to obtain the related analysis data of the music file 13.
The music generator 14 further comprises an instrument database 16 and a synthesis module 18. After obtaining the analysis data from the analysis module 12, the music generator 14 provides the required instrument data 24 from the instrument database 16 according to the analysis data. Then, the synthesis module 18 synthesizes the music. The synthesis module 18 synthesizes a pulse code modulation data according to the analysis data and the instrument data. The digital/analog converter/amplifier 20 converts the pulse code modulation data to an analog signal and amplifies the analog signal. Then, the amplified analog signal is outputted to the speaker 22 to give off sound.
In the wavetable audio synthesis system of the prior art, the basic instrument database includes 128 kinds of melodic instrument data and 47 kinds of percussion instrument data. In the wavetable audio synthesis system of the prior art, the 128 kinds of melodic instrument data and 47 kinds of percussion instrument data are generally stored in a non-volatile memory, such as read only memory (ROM), to be the instrument database. While synthesizing a piece of music, the synthesis module 18 takes the required instrument data out of the instrument database 16 to synthesize the music. Although this method can keep the quality of the synthesized music perfect, the manufacturing cost is usually high because of the large amount of memory required.
The low cost wavetable audio synthesis system of the prior art utilizes certain similarities among some of the instruments, thus storing only the most commonly used instrument data to reduce the cost of storing 128+47 instrument data.
Please refer to FIG. 2. FIG. 2 is a schematic diagram of a low cost wavetable audio synthesis system 30 of the prior art. The low cost wavetable audio synthesis system 30 of the prior art comprises a music database 11, an analysis module 12, a music generator 34, a digital/analog converter/amplifier 20, and a speaker 22. The method of this system 30 is to store M0 kinds of melodic instrument data and P0 kinds of percussion instrument data in a non-volatile memory of lower capacity, and the stored M0 and P0 instruments are representative instruments that are most commonly used. Because the memory capacity of M0+P0 kinds of instrument data is much smaller than that of 128+47 kinds of instrument data, the non-volatile memory of low capacity can be used to reduce cost.
As shown in FIG. 2, the low cost wavetable audio synthesis system 30 of the prior art takes the music file 13 out of the music database 11. Then, the analysis module 12 analyzes the music file 13 to generate an analysis data. The music generator 34 comprises a memory 36, an instrument replacement module 38, and a synthesis module 18. The instrument replacement module 38 performs an instrument replacement procedure after the music generator 34 obtains the analysis data from the analysis module 12. The instrument replacement module 38 contains a similarity comparison table of 128 kinds of melodic instruments and M0 kinds of representative instruments and a similarity comparison table of 47 percussion instruments and P0 representative instruments. By the instrument replacement procedure, the assigned instrument from the analysis data is changed to an instrument among the M0 and P0 kinds of representative instruments. The synthesis module 18 then takes the instrument data 26 out of the memory 36 to synthesize the music.
In the low cost wavetable audio synthesis system of the prior art, the required data of the memory 36 and the instrument replacement module 38 are stored in a non-volatile memory (a non-volatile memory is usually a ROM), so the kinds of instruments, which can be used, are specified. Therefore, there is a disadvantage of compromising the nature of the music due to the selection of the instruments.